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Authors: Leila C. Powell, Scott T. Kay and Arif Babul

Authors: Leila C. Powell, Scott T. Kay and Arif Babul. Substructure in 2D X-ray images and weak lensing mass maps of galaxy clusters: A simulation study. Summary.

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Authors: Leila C. Powell, Scott T. Kay and Arif Babul

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  1. Authors: Leila C. Powell, Scott T. Kay and Arif Babul Substructure in 2D X-ray images and weak lensing mass maps of galaxy clusters: A simulation study

  2. Summary • Make 2D mass maps and X-ray surface brightness maps from cluster simulation to mimic perfect observations • Give statistics on mass substructure and X-ray substructure in 2D • Explore the relation among 2D mass, X-ray SB and 3D subhalo, to give insights into the gas stripping process and interpretations for observational data

  3. Outline • Motivation & Background • Simulation & Data preparation(Map making and substructure detection) • 2D mass map: Completeness and Purity • 2D X-ray map • Discussion (Selection effect, Case study, gas physics, noise-adding) • Conclusion

  4. Motivation & Background • Much Observational Study • X-ray: hot gas (T~1keV) emission • Weak lensing: DM mass • Do not necessarily trace each other: gas stripping • Tidal stripping • Ram pressure • Simulation: • DM subhalo (well-studied) • Gas substructure (not much systematic statistics, and mainly DM-bound gas) • Aim • Provide insight into the link between lensing map and X-ray map through underlying DM distribution • One way to give statistics on gas stripping, through the matching or mismatching of maps • Give predictions/expectations for future observations

  5. Gas Stripping

  6. Motivation & Background • Much Observational Study • X-ray: hot gas (T~1keV) emission • Weak lensing: DM mass • Do not necessarily trace each other: gas stripping • Tidal stripping • Ram pressure • Simulation: • DM subhalo (well-studied) • Gas substructure (not much systematic statistics, and mainly DM-bound gas) • Aim • Provide insight into the link between lensing map and X-ray map through underlying DM distribution • One way to give statistics on gas stripping, through the matching or mismatching of maps • Give predictions/expectations for future observations

  7. Simulation & Data Preparation • Resimulations using GADGET2, standard cosmology • mp(DM)=4.3x10^8 (Msun/h), softening 10 kpc/h (z<1: 5kpc/h) • L~500Mpc/h • z=49~0, 50 outputs • adiabatic • three clusters, ~10^14Msun each, different MAHs • Fof group, R500, SUBFIND subhalo(DM+Gas)

  8. Simulation & Data Preparation • Map making • z=0~1 • Cuboid projection(V=2R500X2R500X8R500),400x400 pixels (pixel size ~ softening) • Re-centered at brightest X-ray pixel

  9. Simulation & Data Preparation • Detection technique • PSF smoothing to get observation • Background making: convolution with a broad filter • Background subtraction • Significance rejectionand FoF group-finding

  10. Simulation & Data Preparation

  11. Simulation & Data Preparation • Properties of 2D map

  12. 2D mass Map vs. 3D sub • Completeness and Obscuration (best: 3sigma)

  13. 2D mass Map vs. 3D sub • Purity (3sigma case)

  14. 2D mass vs. X-ray • A large fraction unmatched

  15. Fraction of subs with little or no hot gas

  16. Scaling relations

  17. Discussion: Selection effect • halo dynamical state (characterized by RMS centroid shift)

  18. Discussion: Case Study • Case I: Partial stripping

  19. Discussion: Case Study • Case II: Detachment • Dependent on numerical techniques (e.g, KHI)

  20. Discussion: Case Study • Case III: missing mass-sub

  21. Discussion: Case Study • Case IV: shared X-ray peak during merger

  22. Discussion: Effect of Cooling • Cooling turned on till z~5, ~10% of gas had formed stars

  23. Discussion: Effect of Cooling • Matching success with cooling

  24. Discussion: adding noise and degraded resolution

  25. Conclusion • Completeness and purity of mass observations • The constructed 2D mass catalogue is 90% complete down to DM mass of 10^13Msun/h ( current weak lensing obs. limit) • Purity threshold of A>10^-3 (Mpc/h)^2, can be applied to other simulated maps • Scaling relation, can be used for mass estimation

  26. Conclusion • A large fraction of substructures unmatched between 2D mass and X-ray, due to detachment or stripping • Dynamical state of clusters plays a role in the fraction of matching success • Inclusion of high-z cooling has only mild impact on the results • Future observations would detect more unmatched substrutures when noise is reduced and resolution enhanced

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